Organic EL devices are able to emit light with a voltage as low as several V to several tens V. Furthermore, organic EL devices are able to emit different color lights by selecting the class of fluorescent organic compounds. Therefore, application of organic EL devices to various light emitting devices and display devices are expected. For example, Unexamined Japanese Patent Application KOKAI Publication Nos. 2001-257075, 2003-26616 and H08-12600 have proposed materials having various structures including fluoranthene and anthracene structures as the host material or light emitting material of blue light emitting devices.
The fluoranthene structure, particularly benzofluoranthene structure yields a significantly high fluorescence intensity and has an energy gap suitable for the host material or light emitting material of blue light emitting devices. Therefore, the fluoranthene structure has always been treated as a blue light emitting material candidate; however, it has not achieved properties suitable for practical use.
On the other hand, the anthracene structure is a significantly potent structure as a highly efficient and long life organic EL host material. Particularly, the anthracene structure plays a key role as the host material of blue light emitting devices. However, since blue light emitting devices having a much longer life is demanded and slight change in physical properties is required for dealing with more complex device structures, the anthracene structure is not always a satisfactory blue light emitting material.
Cross-coupling of materials of different structures is considered to be a means for developing a new material for dealing with such slight change in physical properties. Combing two different structures, cross-coupling allows their respective properties to realize in one material, covering a wider range of device structures. A combination of benzofluoranthene and anthracene structures can be a potent combination as a blue light emitting material.